1. Field of the Invention
The present invention relates generally to a member employed corresponding to a product storage container used for storing an object such as a semiconductor, a panel for a flat panel display and an optical disc in a process of manufacturing the object undergoing a process under a high-purity environment, i.e., corresponding to the container retained in a state where an internal pressure thereof is different from an ambient pressure. The present invention relates to more particularly to a so-called interface seal (which will hereinafter be referred to as a seal member) used when connecting the container, which is a so-called FOUP (Front-Opening Unified Pod) employed to store 300 mm semiconductor wafers each having a diameter of 300 mm mainly in a processing step of the 300 mm semiconductor wafers, to a gas replacement system for replacing a gas sealed in an interior of the container.
2. Related Background Art
A connecting portion between the FOUP and the gas replacement system connected to the FOUP is, as described above, exemplified by way of a specific example using the seal member according to the present invention. In such a usage example, especially a stable sealing characteristic with respect to an ambient environment is required of the seal member. Accordingly, on the occasion of describing the present invention, particularly technologies related to the FOUP will be descried as exemplifications of the prior arts.
In the semiconductor device manufacturing process, high purification required in the process has hitherto involved attaining cleanliness of rooms in the whole factory for conducting a variety of processes for the wafers. With a larger diameter of the wafer, this type of measure leads to a problem of cost for acquiring the (high-purity) environment in terms of the construction. Over the recent years, there have been adopted means for ensuring mini-environment spaces kept in a high degree of purity for each of the processing apparatuses.
To be specific, a scheme is not to enhance the degree of purity of the whole factor but to keep in the high degree of purity only an interior of each processing apparatus in the manufacturing process and an interior of a storage container (which will hereinafter be called a pod) while being carried. This pod is, as described above, generically referred to as the FOUP. Thus, the same effect as by attaining the cleanliness of the rooms of the whole factory, is acquired by adopting a so-called mini-environment system that highly purifies only slight amounts of spaces, thereby actualizing an efficient production process in a way that reduces an investment for equipment and a maintenance cost as well.
A semiconductor processing apparatus etc corresponding to the so-called mini-environment system will hereinafter be briefly described. The semiconductor wafer processing apparatus mainly includes a Loadport portion in which to perform operations of placing a pod for inserting and removing the wafer and opening/closing a cover of the pod, a carrier chamber in which a robot is disposed inside and carries the wafer, and a processing chamber in which the wafer is received from the robot and subjected to a variety of processes. The respective joined portions are sectioned respectively by corresponding pieces of partitions and covers. In the carrier chamber of the semiconductor wafer processing apparatus, an air flow is generated by a fan provided at an upper portion of the carrier chamber toward a lower part from an upper part of the carrier chamber in order to keep the high degree of purity by purging the carrier chamber of dusts. The existence of the air flow causes the dusts to be discharged toward the lower side at all times.
Above the Loadport portion, the pod defined as the storage container for a stored product such as a silicon wafer (which will hereinafter simply be termed a wafer) is secured onto a predetermined mounting plate. As described earlier, the interior of the carrier chamber is kept in the high degree of purity for processing the wafer, and the robot is disposed inside the carrier chamber. The wafer is carried by the robot arm between the interior of the pod and the interior of the processing chamber. The processing chamber normally includes a variety of mechanisms for executing the processes such as forming a thin film on the wafer surface and processing the thin film, however, descriptions of the constructions thereof, which are not related directly to the present invention, are therefore omitted herein.
The pod has a space for internally accommodating the wafer defined as an object to be processed. The pod includes a box-shaped main body portion having an opening portion on any one of surfaces, and a cover for airtightly closing the opening portion. A multi-staged rack for stacking the wafers in one direction is disposed in an interior of the main body portion. The pod internally accommodates the wafers placed at a fixed interval in the rack. Note that the direction of stacking the wafers is set in a perpendicular direction in the FOUP exemplified herein. An opening portion is provided on the side of the Loadport portion of the carrier chamber. The opening portion is disposed in a position having a face-to-face relationship with the opening portion of the pod when the pod is disposed above the Loadport portion so as to get close to the opening portion. An opener is provided in the vicinity of the opening portion inwardly of the carrier chamber. After the opener has taken the cover out of the pod, the wafer is carried in or carried out by the robot arm.
Normally, a recessed portion, an intake port and an exhaust port are provided at the lower portion of the pod. The plate surface is provided with a positioning pin that regulates a pod mounting position by fitting in the recessed portion, a plate-side intake port abutting on the pod-side intake port, and a plate-side exhaust port abutting on the pod-side exhaust port. Seal members for enhancing air-tightness of abutting portions at which the plate-side intake/exhaust ports abut on the pod-side ports, are disposed in the opening portions of the plate-side intake/exhaust ports. Filter members are disposed in the vicinities of the opening portions of the pod-side intake/exhaust ports, thereby preventing dusts etc from entering the interior of the pod via the ports. The intake port and the exhaust port on the plate side are connected via respective check valves and flow meters to a replacement gas supply source and to a replacement gas discharge source as external devices.
For instance, Japanese Patent Application Laid-Open No.2002-531934 or Japanese Patent Application Laid-Open No.8-203993 discusses outlines of the constructions described above. Normally, the wafer restrained from adhesion of the dusts is brought into the pod for accommodating the products, and an internal atmosphere of the pod is replaced by an inert gas such as clean nitrogen, thus restraining occurrence a chemical change caused by natural oxidation or organic contamination over the wafer surface in an accommodated state. Such an internal atmosphere replacing operation is conducted via a gas flow path formed extending from the intake/exhaust ports provided in the pod and the plate in the state where the pod is mounted on the plate. Accordingly, the gas flow path is required to have a size enabling a sufficient amount of replacement gas or internal atmosphere to flow, and is required to ensure sufficient tightness for preventing the replacement gas or the internal atmosphere from being contaminated. The seal members used at these intake/exhaust ports are therefore demanded to ensure the sufficient sealing characteristic that meet these requirements.
So-called packing taking a ring-like shape has hitherto been utilized as the seal member. FIGS. 8A and 8B illustrate schematic sectional views of the pod-side exhaust (intake) port and the plate-side exhaust (intake) port in the case of using the packing. FIG. 8A illustrates a case of using a seal member 18a taking a so-called domed shape having a curved internal surface shape of which an inside diameter gets smaller as it gets closer to an upper opening. FIG. 8B illustrates a case of using a seal member 18b taking a so-called funnel-like shape having a curved internal surface shape of which an inside diameter gets larger as it gets closer to the upper opening.
If a pressure within the packing, i.e., a pressure on the side of the gas flow path is larger than a pressure outside the packing, a pressure causing the domed shape to deform outside is applied to the seal member 18a illustrated in FIG. 8A. A case of using the seal member 18a on the side of the intake port is considered as this situation. In this case, a deforming pressure is applied to the sealing surface of the seal member 18a so as to tightly fit to a port edge portion on the pod side, whereby the sealing characteristic is more strengthened and stabilized. Whereas if the internal pressure of the packing is smaller than the outside pressure, namely in the case of employing the seal member 18a on the side of the exhaust port, the deforming pressure causing the domed shape to deform inside as indicated by an arrowhead in FIG. 8A, is applied due to this pressure difference. As a result, the tight fitting characteristic between the sealing surface of the seal member 18a and the pod-side port edge portion decreases, and it is also considered that a gap etc occurs in an extreme case.
If the internal pressure of the packing is smaller than the external pressure of the packing, a pressure causing the funnel-like shape to deform inside is applied to the seal member 18b illustrated in FIG. 8B. A case of using the seal member 18b on the side of the exhaust port is considered as this situation. In this case, a deforming pressure is applied to the sealing surface of the seal member 18b so as to tightly fit to the port edge portion on the side of the pod 2, whereby the sealing characteristic is more strengthened and stabilized. Whereas if the internal pressure of the packing is larger than the outside pressure, namely in the case of employing the seal member 18a on the side of the intake port, the deforming pressure causing the funnel-like shape to deform outside as indicated by an arrowhead in FIG. 8B, is applied due to this pressure difference. As a result, the tight fitting characteristic between the sealing surface of the seal member 18b and the pod-side port edge portion decreases, and it is also considered that the gap etc occurs in the extreme case.
It is therefore difficult to share the dome-shaped seal member and the funnel-shaped seal member with each other. The dome-shaped seal member and the funnel-shaped seal member are required to be used separately depending on a positive pressure or a negative pressure taken by a should-be-sealed environment (which will hereinafter be termed an intra-seal environment). The environment in which the seal member should be provided generally changes in pressure, and hence the individual sealing characteristic changes as the environment pressure changes. It is therefore necessary for the seal member to deform at a fixed or larger level in a way that applies a load large enough to crush the seal member in order to ensure the fixed sealing characteristic. In this case, though required to apply the large load, such a problem arises that the seal member gets into plastic deformation as the seal member repeatedly gets deformed, resulting in a high frequency of exchanging the seal member. At the same time, what is demanded for ensuring the preferable sealing characteristics by uniform deformations of the seal members is to always keep pod-side surface accuracy, plate-side surface accuracy and further accuracy of the sealing surface of the seal member. This brought about a rise in cost for processing these members.
Japanese Patent Application Laid-Open No. 2002-510150, U.S. Pat. No. 6,164,664 or U.S. Pat. No. 5,988,233 discuss a curved domed grommet or a bellow type seal member for the purpose of preventing the plastic deformation caused by repeatedly applying the load. These configurations seem to exhibit the preferable effects in terms of preventing the plastic deformation. It is, however, considered that none of particular effects are exhibited to cope with such a problem to be solved by the present invention that the sealing characteristic changes due to the change in pressure of the intra-seal environment.